Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02364755 2001-12-12
The invention concerns a fuel tank and more particularly a fuel tank
for a motor vehicle.
A typical form of fuel tank for a motor vehicle comprises a filling
opening for introducing fuel into the tank in a refuelling procedure, at least
one fuel delivery pump to feed fuel from the fuel tank to the engine of the
motor vehicle, and at least one operational vent means and at least one
refuelling vent means.
It will be noted in that respect at this point that the term operational
vent means is used herein to denote a vent means for venting the fuel tank
during operation of the vehicle, for venting fuel vapor for example from the
tank due to fluctuations in temperature or caused by swirl or surge
movements of the fuel in the fuel tank in response to dynamic movement
of the motor vehicle in which the fuel is disposed. The term refuelling vent
means is used herein to denote a vent means operative to vent the tank
upon a tank filling or refuelling procedure.
The vent means are connected to a fuel vapor filter by way of at
least one vent line while connected upstream of the fuel vapor filter is at
least one bead removal container for removing liquid beads or droplets of
fuel from the fuel vapors carried in the vent line.
It will be appreciated that fuel tanks of the above-indicated general
configuration which nowadays are usually formed in one or more pieces
from plastic material are systems which are optimised in terms of
hydrocarbon emissions. As is known, certain plastic materials, for example
polyethylene, are permeable in relation to hydrocarbons. For that reason,
fuel tanks of plastic material are often of a multi-wall configuration or are
made from multi-layer extrudates with incorporated barrier layers for
hydrocarbons to prevent diffusion thereof through the wall of the tank to
the surrounding atmosphere. It is in the meantime possible for fuel tanks of
plastic material for hydrocarbon fuels to be designed in such a way as to be
very substantially diffusion-resistant in relation to such fuels. Possible
sources of hydrocarbons emissions however are still connecting nipples,
valves, hoses, fitting openings and the like on or in the tank wall. It will
be
appreciated that lines and conduits going to and from the fuel tank also
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CA 02364755 2001-12-12
constitute possible sources of fuel emission. It is therefore desirable for as
few connections and like components to be provided on a fuel tank and for
as many other units of equipment which are required to ensure a supply of
fuel to an internal combustion engine of a motor vehicle to be disposed in
the interior of the fuel tank.
It will further be appreciated that manufacturing and assembly costs
for fuel tanks and fuel feed systems which are optimised in terms of fuel
emissions are to be kept within reasonable limits, either in the case of fuel
tanks of plastic material which are made in one or more parts or in the case
of fuel tanks of metal which are similarly made up of a plurality of parts.
In the case of multi-part fuel tanks comprising two or more casing
portions, arranging a large part of the lines and other units of equipment
for providing for the supply of fuel to the motor vehicle engine in the
interior of the fuel tank and fixing them therein will involve a comparatively
low level of assembly expenditure. That however is a more difficult
proposition in the case of one-piece plastic fuel tanks which are formed by
extrusion blow molding. In the case of such a fuel tank the body of the tank
has to be blow-molded in part around the installation units in the procedure
for producing the tank or the installation units have to be subsequently
2o fitted into the tank through fitting openings which are to be subsequently
gas-tightly closed.
Although the installation units of the fuel tank and the fuel supply
system which is to be provided thereon are to be designed to last the
service life of the fuel tank, it is nonetheless often desirable to reduce the
number of components used and to make some components such as for
example the fuel pump or a suitable fuel delivery unit interchangeable for
repair or maintenance purposes.
In accordance with the present invention there is provided a fuel
tank for a motor vehicle, comprising at least one filling opening, at least
one fuel delivery pump, at least one operational vent means, at least one
refuelling vent means, a fuel vapor filter, at least one vent conduit
connecting the vent means to the fuel vapor filter, at least one bead
removal container, and means connecting the bead removal container on
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CA 02364755 2001-12-12
the upstream side of the fuel vapor filter, wherein at least the bead
removal container and the at least one refuelling vent means are combined
to form a functional unit in the form of a vent unit.
As will be seen in greater detail from an embodiment of a fuel tank in
accordance with the present invention as described hereinafter combining a
plurality of components of the vent system of the fuel tank to constitute a
unit can simplify assembly of the tank and minimise the number of
connections of the entire vent system. If the fuel tank is made from plastic
material, which is the preferred option here, the vent unit provided in
accordance with the invention can contribute to reducing the number of
connecting locations and weld locations involved in the vent system. A
further advantage of this arrangement is that this involves a significant
number of the connecting locations involved in the assembly being moved
into the tank, which makes a quite considerable contribution to reducing
hydrocarbon emissions.
In a preferred feature of the invention the vent unit is arranged
overall releasably and interchangeably in the fuel tank. In that way, if the
vent unit has for example a defective valve, it can be quite readily replaced
or repaired. In a further preferred feature the vent unit can be in the form
2o of an insert which is adapted to close a fitting opening in the wall of the
fuel
tank.
The vent unit can be for example in the form of a cover closure
which is sealed with a cover flange in relation to the tank wall. The cover
flange can then be welded to the tank wall. Alternatively, it can be provided
that the cover flange is braced in relation to the tank wall by means of a
union nut, with the interposition of one or more seals. In that case, a
suitable screwthreaded connecting portion or an additional screwthreaded
ring is to be provided in or on the tank wall.
It will be appreciated that both the fuel feed afforded by the fuel
delivery system to the motor vehicle engine and possibly the return
therefrom can be taken through the above-mentioned cover closure of the
vent unit. It may also accommodate cable ducting means for the fuel
delivery pump, a sender such as a fuel level sensor and the like. This
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CA 02364755 2001-12-12
affords the advantage that it is possible to save on an additional cover
closure and an additional fitting opening for the fuel delivery unit, whereby
the number of openings in a diffusion-tight tank wall can also be reduced.
In that case the fuel delivery unit can be fitted into the fuel tank through
the fitting opening for the vent unit.
In a further preferred feature of the invention the cover closure is in
the form of a carrier means for the vent unit.
In a further preferred feature of the invention the fuel tank includes
at least one roll-over valve in the vent unit, more preferably disposed in the
immediate proximity of the cover closure. In the installation position of the
tank, the roll-over valve would be arranged approximately in the upper
third of the bead removal container adjoining the cover closure.
In still another preferred feature of the invention at least one safety
pressure relief valve can be disposed in the vent unit, operable to permit
emergency venting of the fuel tank when the operational vent means and
the refuelling vent means are closed. Such a safety valve for example
prevents an excessively increased pressure from building up in the fuel
tank in the case of the tank being overfilled. It is therefore appropriate for
the safety valve to be provided on the vent unit in such a way that the
safety valve is disposed in the gas phase in the fuel tank, when the vehicle
is in any reasonably possible inclined position.
Preferably, there are a plurality of operational vent means which are
connected to the vent unit by way of a common vent conduit or a plurality
of vent conduits. The vent unit thus also serves to bring together all the
vent ducts from the fuel tank.
The operational vent means can be in the form of operational vent
valves with or without a pressure-holding function or alternatively in the
form of simple vent nipples.
Desirably, the refuelling vent means is in the form of a refuelling
vent valve, but it is also possible to provide a shut-off valve in the filler
pipe of the fuel tank, to actuate a shut-off mechanism of a refuelling gun in
order thereby to terminate a refuelling procedure, so that the refuelling
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CA 02364755 2001-12-12
vent means does not have to involve any shut-off function or any pressure
holding function.
A preferred configuration in accordance with this invention however
provides that the operational vent means and also the refuelling vent
means are in the form of valves. In that case the operational vent means
will be such as to close due to actuation by a float when fuel is present
thereat. A pressure holding function for the operational vent valve is
ensured by a pressure relief valve disposed on the downstream side
thereof.
The bead removal container is desirably provided with a labyrinth
configuration or with internally disposed baffle walls so that liquid
hydrocarbons contained in dispersed form in the fuel vapors can condense
out in the bead removal container. The bead removal container is to be
provided for the reason that in dynamic operation of the motor vehicle in
which the fuel tank of the invention is fitted or when refuelling the motor
vehicle, it is not impossible for a mixture of liquid and gaseous fuel to be
entrained by way of the vent conduits. It is appropriate to avoid as far as
possible liquid hydrocarbons being passed to the fuel vapor filter as that
can adversely affect the regeneratability thereof. In general such a fuel
vapor filter is in the form of an activated carbon filter which is regenerated
by way of the combustion air feed to the engine.
In accordance with the invention it is preferably provided that the
refuelling vent valve is arranged immediately beneath the bead removal
container or on same at the upstream side thereof. The valve casing
surrounding the refuelling vent valve, like the bead removal container, can
be provided with labyrinth fitments therein.
As in accordance with the invention the bead removal container can
be arranged in the fuel tank, it is not impossible that, when there is a high
level of fuel in the tank, there is no or only a slight difference in level
between the level of liquid in the bead removal container and the level of
fuel in the fuel container. In that case, it is preferable to provide means
for
actively emptying the bead removal container into the fuel tank against a
fall in level or when there is a slight difference in level between the level
of
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fuel in the fuel tank and the level of liquid in the bead removal container.
In
that case the operational vent means can be in the form of one or more
nipples, in which respect it is possible to accept that a certain amount of
liquid hydrocarbons passes into the bead removal container by way of the
vent means. The volume of the bead removal container can be such that
the entrainment of liquid hydrocarbons through the vent conduits into the
bead removal container can be tolerated within certain limits.
For the purposes of actively emptying the bead removal container
into the fuel tank, it is possible for example to connect a drain conduit
1o thereof to the suction intake side of a pump, for example a suction jet
pump. The suction jet pump can be operated in the manner known in
relation to such devices, by way of a flow portion of fuel which is branched
off the flow of fuel being conveyed to the engine. Alternatively, it is
possible
for example in the case of a fuel delivery system with a return from the
engine, for the suction jet pump to be operated by way of the return flow
from the engine. It is preferable to provide an additional suction jet pump
for the purposes of actively emptying the bead removal container.
Depending on the respective configuration of the fuel tank which can be of
a complex structure involving a plurality of filling levels therein, for
example in different compartments of the tank, suction jet pumps are often
to be provided in any case for emptying various compartments in the tank
into the reservoir or swirl pot of a fuel delivery unit of the tank.
An embodiment of the invention will now be described by way of
example with reference to the accompanying drawing in which:
Figure 1 is a diagrammatic view of a fuel tank according to the
invention in operation of a motor vehicle in which the fuel tank is fitted,
and
Figure 2 is a diagrammatic view of the Figure 1 fuel tank during a
refuelling procedure.
Referring generally at this stage to the drawings reference numeral 1
therein denotes a fuel tank which in this embodiment is in the form of a
plastic fuel tank produced by extrusion blow molding. It includes a filler
pipe or filler connection 2 and a fuel delivery unit 3 disposed in the
interior
of the fuel tank 1. It will be appreciated that the fuel tank 1 may comprise
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CA 02364755 2001-12-12
metal or a plurality of injection-molded casing portions which are suitably
assembled to constitute the tank body.
The fuel delivery unit 3 includes a surge or swirl pot
diagrammatically indicated at 4 as a fuel reservoir and a delivery pump
(not shown) which is arranged therein. Reference numeral 5 denotes a first
suction jet pump which is operable during operation of the engine of the
motor vehicle to convey fuel from the free volume of the fuel tank into the
surge pot 4. From there, the fuel delivery pump which is part of the fuel
delivery unit 3 conveys the fuel to the engine of the motor vehicle, by way
of a fuel feed which is diagrammatically indicated at 6. It will be noted at
this point that the fuel delivery pump can be arranged inside or outside the
fuel tank 1, with either of those positions falling within the invention.
Arranging the fuel delivery pump within the fuel tank in the manner
described and illustrated herein is however the preferred option.
It will be appreciated that a fuel tank requires vent means which on
the one hand provide for venting thereof during a tank refuelling procedure,
while on the other hand ensuring continuous venting as the fuel in the fuel
tank outgasses due for example to an increase in temperature and due to
motion dynamics when the motor vehicle in which the fuel tank 1 is
installed is moving, causing swirl and surge movements of the fuel in the
fuel tank 1. Not least also is the fact that the fuel must be capable of
expanding as a result of temperature fluctuations.
To provide for venting of the fuel tank 1 during operational
movement of the motor vehicle, this being referred to herein as operational
venting, provided in the fuel tank 1 in the region of the wall which is the
upper wall thereof in the installation position of the fuel tank 1 is at least
one operational vent means as indicated at 7, and preferably, as illustrated,
a plurality of such operational vent means. Thus, the drawing
diagrammatically shows just two operational vent means 7, but it will be
apparent that these can be provided at the most widely varying locations in
relation to the fuel tank, as much as possible in the gaseous phase of the
fuel, in other words, in the region of the fuel tank which is an upper region
in the installation position thereof, in the proximity of the upper wall of
the
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fuel tank. In the illustrated embodiment the operational vent means 7 are
in the form of operational vent valves which only respond by opening when
there is an increased pressure in the fuel tank 1, but which close, for
example under the actuation of a float device, when fuel approaches,
caused for example by surge and swirl movements of the fuel in the fuel
tank 1. Alternatively it is possible for the operational vent means 7 to be in
the form of simple nipples which are connected by way of vent conduits
indicated at 8a to a vent unit which is identified generally by reference
numeral 9. It will be further appreciated that it is possible to provide both
a
plurality of vent conduits 8a and also alternatively a common collector vent
conduit.
The vent unit 9 includes a bead removal container 10 which has
labyrinth-type fitments therein and to which all inwardly disposed vent
conduits 8a are connected. A further integral component of the vent unit 9
is a refuelling vent valve 1l which is disposed in a valve chamber 12. The
valve chamber 12 is connected directly to the bead removal container 10.
In the illustrated embodiment, the valve chamber 12 communicates with
the bead removal container 10 by way of the refuelling vent valve 1l which
is disposed at an upward position in the valve chamber. The refuelling vent
valve 11 is in the form as illustrated of a spring-loaded float valve which is
usually open in operation of the vehicle in which the fuel tank 1 is fitted,
unless the planned maximum filling level of fuel in the fuel tank 1 is
reached. When the level of fuel in the fuel tank 1 rises during the course of
a refuelling procedure, the float of the refuelling vent valve 11 is lifted
into
the closed position so that, in the refuelling procedure, an increased
pressure is built up in the fuel tank 1 and causes a refuelling gun valve to
be shut off at that stage in the refuelling procedure. As already mentioned
above, the operational vent means 7 are desirably in the form of valves
which afford a pressure holding function in order ultimately to ensure the
rise in pressure within the fuel tank 1 in order to actuate the shut-off
mechanism of the refuelling gun in order thereby to terminate the refuelling
procedure.
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The bead removal container 10 is provided with a drain conduit 11
which opens into the fuel tank 1 and by way of which the bead removal
container 10 can be emptied into the fuel tank 1. In order to prevent the
fuel from the fuel tank 1 from flowing into the bead removal container 10
by way of the drain conduit 13, a check valve 14 is suitably provided in the
drain conduit 13.
In order to guarantee that the bead removal container 10 is still
certain to be emptied of fuel when there is a high level of fuel in the fuel
tank 1, the drain conduit 13 is connected to the suction intake side of a
second suction jet pump 15. Although the structure and mode of operation
of a suction jet pump such as those indicated at 5 and 15 in the drawings
will be generally familiar aspects, the mode of operation thereof will be
nonetheless briefly discussed herein.
The fuel tank 1 is shown here in simplified form as being of
approximately rectangular cross-section. It will be noted however that the
fuel tank can be of many different configurations involving different filling
levels and entailing different planes and compartments in the tank. Usually,
suction jet pumps are provided in fuel tanks to ensure that fuel is
continuously conveyed from the main body or compartment of the fuel tank
1 into the surge or swirl pot 4 from which fuel is fed to the fuel pump, so as
to ensure that the surge or swirl pot 4 is continuously filled with fuel and
thus also to ensure a constant supply of fuel to the fuel pump and thus the
engine of the motor vehicle. A drive jet which can be formed by a flow of
fuel taken from the feed to the engine or the return from the engine is
operable in the suction jet pump to produce a reduced pressure in the
region of a flow constriction in the manner of a venturi nozzle. A suction
conduit opens into the region of the narrowest flow cross-section of the
venturi nozzle, or into a suction chamber disposed at that location. The
reduced pressure in the venturi nozzle thus draws fuel into same from the
suction conduit. In that region therefore the drive jet which is passed
through the suction jet pump is combined with the flow of fuel which is
drawn thereinto.
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As already indicated above fuel tanks will mostly include a plurality of
such suction jet pumps. In the case of a fuel delivery system which does
not involve a return flow of fuel from the engine to the tank, as is shown
herein without however limitation thereto, the drive jet of the suction jet
pump is branched off the fuel feed 6 to the engine by way of a pressure
regulating valve diagrammatically indicated at 23. Both the first suction jet
pump 5 and also the second suction jet pump 15 are operated in parallel
relationship by way thereof. The second suction jet pump 15 acts at its
suction side on the bead removal container 10 by way of the check valve
i0 14. The first suction jet pump 5 is operable to deliver fuel from the fuel
tank 1 into the surge or swirl pot 4.
From the vent unit 9, only a single vent conduit 8b goes to a fuel
vapor filter 24. Connected upstream of that portion of the vent valve 8b, in
the vent unit 9 or in the bead removal container 10, is a valve referred to
i5 as a roll-over valve as indicated at 16. The roll-over valve 16 is in the
form
of a float-actuated valve and/or a gravity-actuated valve and seals off the
entire system in the event of the motor vehicle rolling over, in that case
more specifically the roll-over valve 16 responding in a gravity-actuated
mode. The tank also has a safety valve which is diagrammatically indicated
20 at 17 and which for example in the event of the fuel tank 1 being
overfilled,
with an unacceptable increase in pressure therein, permits venting of the
tank, more specifically when the operational vent means 7 and also the
refuelling vent valve 1i are in a closed condition.
The safety valve 17 is so arranged, in the installation position of the
25 fuel tank 1 and the vent unit 9, that as far as possible the safety valve
is
disposed in the gas phase of the fuel when the operational vent means 7
are immersed in fuel and accordingly closed, in order thereby to ensure a
venting effect even when the fuel tank 1 is in an extreme inclined position.
It will be seen from the drawings that the vent unit 9 is in the form
30 of a functional unit for closing a fitting opening indicated at 18 in the
upper
wall of the fuel tank 1.
In the illustrated structure the fitting opening 18 is provided at the
edge of the fuel tank 1, but alternatively it can also be arranged at a
CA 02364755 2001-12-12
spacing from the edge and for example at a central position. The vent unit
9 is provided with an outwardly disposed cover closure 19 which carries the
entire assembly comprising the bead removal container 10, the valve
chamber 12 and the valves arranged therein, as a construction unit. The
cover closure 19 bears with a cover flange 20 against the outer wall 21 of
the fuel tank. The cover flange 20 can be secured as by welding to the tank
wall 21.
Alternatively, to make it readily possible to replace the vent unit 9 if
required the cover closure 19 can be braced with its cover flange 20 against
the tank wall 21 for example by means of a union nut (not shown), with the
interposition of at least one sealing means. The closure arrangement may
also advantageously be of a configuration as is described in US patent
application Serial No 08/886001 (US patent No ) to which reference
is directed in respect of the full content thereof for the purposes of
incorporating the disclosure of same into the present specification.
Finally, the drawings also show a pressure conduit which is indicated
by reference 22 which ensures that the filler pipe 2 can be subjected to the
action of a pressure by way of the vent unit 9 for diagnosis purposes, using
on-board diagnostics for checking sealing integrity.
2o It will be noted that the drawings show the check valve 14 as being
disposed outside the vent unit 9. It will be appreciated however that the
check valve 14 may also be an integral component part of the vent unit 9.
It will be seen from the foregoing that the present invention can
provide a fuel tank for a motor vehicle, which is improved in terms of its
emission values, while further being simplified in respect of its structure.
The motor vehicle fuel tank involves a reduction in connecting locations and
like units which are liable to constitute a source of emission from the tank
and it can further be so designed that a significant proportion of
connections thereon are moved into the tank so as to make a considerable
contribution to reducing possible hydrocarbon emissions therefrom. The
fuel tank also affords enhanced ease of replaceability of fuel tank
components which are liable to require repair and/or maintenance.
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It will be appreciated that the above-described embodiment of the
invention has been set forth solely by way of example and illustration of the
principles thereof and that various modifications and alterations may be
made therein without thereby departing from the spirit and scope of the
invention.
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